Metal structures are common throughout industry due to their ease of construction, strength and mechanical integrity. A common problem is faced when attempting to communicate data across the body of a metal structure. A hole can readily be drilled to pass through an electrically conductive or optical fibre communications cable, but this results in a weakening of the otherwise continuous metal barrier and introduces an area, which is often prone to failure. In extreme applications, such as the metal pressure hull of a submerged vehicle, failure of such a through hole penetration can have serious operational consequences. There is a need for a system that can effectively extend communications and power distribution in to areas bounded by a metal barrier without the need to modify the barrier.